Reaction and temperature control for high power microwave-assisted chemistry techniques

Abstract

A method is disclosed for carrying out microwave assisted chemical reactions. The method includes the steps of placing reactants in a microwave-transparent vessel, placing the vessel and its contents into a microwave cavity, applying microwave radiation within the cavity and to the vessel and its contents while concurrently externally cooling the vessel conductively.

What is claimed is:  
     
       1. A method of carrying out microwave assisted chemical reactions, the method comprising: 
       placing reactants in a microwave-transparent vessel;  
       placing the vessel and its contents into a microwave cavity; and  
       applying a continuous single mode of microwave radiation within the cavity and to the vessel and its contents while concurrently externally cooling the vessel.  
     
     
       2. A method according to  claim 1  comprising placing the reactants in a pressure-resistant vessel and sealing the vessel prior to the step of applying the microwave radiation. 
     
     
       3. A method according to  claim 1  comprising concurrently measuring the temperature of the vessel or its contents while applying the microwave radiation. 
     
     
       4. A method according to  claim 1  wherein the step of placing the vessel and its contents into the microwave cavity comprises robotic transfer of the vessel. 
     
     
       5. A method according to  claim 1  comprising applying the microwave radiation from a source selected from the group consisting of magnetrons, klystrons and solid state sources. 
     
     
       6. A method according to  claim 3  wherein the step of cooling the vessel and its contents comprising directing an air flow over the vessel at a rate sufficient to maintain the vessel and contents at a desired temperature. 
     
     
       7. A method according to  claim 6  comprising directing the air flow intermittently. 
     
     
       8. A method according to  claim 6  comprising changing the rate of air flow in response to the measured temperature. 
     
     
       9. A method according to  claim 6  comprising directing the air flow at a rate of between about 1 and 80 psi. 
     
     
       10. A method according to  claim 1  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 60 hertz. 
     
     
       11. A method according to  claim 1  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 600 hertz. 
     
     
       12. A method according to  claim 1  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 6000 hertz. 
     
     
       13. A method according to  claim 1  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of between about 10,000-250,000 hertz. 
     
     
       14. A method according to  claim 1  comprising cooling the vessel continuously. 
     
     
       15. A method according to  claim 1  wherein the step of applying a single mode of microwave radiation comprises propagating the microwaves into a cavity that limits the radiation to a single mode. 
     
     
       16. A method of carrying out microwave assisted chemical reactions, the method comprising: 
       placing reactants in a microwave-transparent pressure resistant vessel and sealing the vessel;  
       placing the sealed vessel and its contents into a microwave cavity;  
       applying microwave radiation continuously within the cavity and to the vessel and its contents;  
       while monitoring the temperature of the vessel; and  
       while concurrently externally cooling the sealed vessel and its contents.  
     
     
       17. A method according to  claim 16  wherein the step of placing the vessel and its contents into the microwave cavity comprises robotic transfer of the vessel. 
     
     
       18. A method according to  claim 16  comprising applying the microwave radiation from a source selected from the group consisting of magnetrons, klystrons and;solid state sources. 
     
     
       19. A method according to  claim 16  wherein the step of cooling the vessel and its contents comprising directing an air flow over the vessel at a rate sufficient to maintain the vessel and contents at a desired temperature. 
     
     
       20. A method according to  claim 19  comprising directing the air flow intermittently. 
     
     
       21. A method according to  claim 19  comprising changing the rate of air flow in response to the measured temperature. 
     
     
       22. A method according to  claim 19  comprising directing the air flow at a rate of between about 1 and 80 psi. 
     
     
       23. A method according to  claim 16  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 60 hertz. 
     
     
       24. A method according to  claim 16  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 600 hertz. 
     
     
       25. A method according to  claim 16  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 6000 hertz. 
     
     
       26. A method according to  claim 16  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of between about 10,000-250,000 hertz. 
     
     
       27. A method according to  claim 16  comprising cooling the vessel continuously. 
     
     
       28. A method of carrying out microwave assisted chemical reactions, the method comprising: 
       placing reactants in a microwave-transparent vessel;  
       placing the vessel and its contents into a microwave cavity;  
       monitoring the temperature of the vessel or its contents; and  
       applying a continuous single mode of microwave radiation within the cavity and to the vessel and its contents until the temperature reaches a desired setpoint; and  
       concurrently externally cooling the vessel and its contents while applying the continuous microwave radiation to maintain the temperature substantially at the setpoint.  
     
     
       29. A method according to  claim 28  comprising placing the reactants in a pressure-resistant vessel and sealing the vessel. 
     
     
       30. A method according to  claim 28  comprising continuously monitoring the temperature. 
     
     
       31. A method according to  claim 28  comprising initiating the cooling step when the monitored temperature reaches a designated setpoint. 
     
     
       32. A method according to  claim 28  wherein: 
       the cooling step comprises cooling the vessel with a fluid from a fluid source; and  
       the step of applying the microwave radiation comprises maximizing the microwave power at the capacity of the cooling source while maintaining the temperature substantially at the set point.  
     
     
       33. A method according to  claim 28  comprising changing the desired setpoint and carrying out the steps of applying microwave radiation and external cooling to reach and maintain the temperature at the new setpoint. 
     
     
       34. A method according to  claim 28  wherein the step of placing the vessel and its contents into the microwave cavity comprises robotic transfer of the vessel. 
     
     
       35. A method according to  claim 28  comprising applying the microwave radiation from a source selected from the group consisting of magnetrons, klystrons and solid state sources. 
     
     
       36. A method according to  claim 28  wherein the step of cooling the vessel and its contents comprising directing an air flow over the vessel at a rate sufficient to maintain the vessel and contents at a desired temperature. 
     
     
       37. A method according to  claim 36  comprising directing the air flow intermittently. 
     
     
       38. A method according to  claim 36  comprising changing the rate of air flow in response to the measured temperature. 
     
     
       39. A method according to  claim 36  comprising directing the air flow at a rate of between about 1 and 80 psi. 
     
     
       40. A method according to  claim 28  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 60 hertz. 
     
     
       41. A method according to  claim 28  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 600 hertz. 
     
     
       42. A method according to  claim 28  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of greater than 6000 hertz. 
     
     
       43. A method according to  claim 28  wherein the step of applying continuous microwave radiation comprises applying radiation from a source and driving the source at a frequency of between about 10,000-250,000 hertz. 
     
     
       44. An instrument for carrying out microwave assisted chemical reactions, said instrument comprising: 
       a microwave cavity;  
       a microwave-transparent vessel in said cavity;  
       a detector for monitoring the temperature of said vessel or its contents in said cavity;  
       means for applying a continuous single mode of microwave radiation within said cavity and to said vessel and its contents until the temperature reaches a desired setpoint as measured by said detector; and  
       means for concurrently externally cooling said vessel and its contents while applying the continuous microwave radiation; and  
       means for maintaining the temperature substantially at the setpoint while applying the microwave radiation.  
     
     
       45. An instrument according to  claim 44  wherein said microwave applying means comprises a source and a waveguide in communication with said source and said cavity. 
     
     
       46. An instrument according to  claim 44  wherein said temperature maintaining means comprises a processor in signal communication with said detector. 
     
     
       47. An instrument according to  claim 46  wherein said cooling means comprises a source of cooling fluid and a fluid communication path from said source to said cavity. 
     
     
       48. An instrument according to  claim 47  wherein said temperature maintaining means further comprises a flow controller in signal communication with said processor and in fluid communication with said fluid source and said cavity for moderating the flow of fluid from said source to said cavity in response to signals from said processor. 
     
     
       49. An instrument according to  claim 48  wherein said processor controls said flow controller in response to temperature data from said detector. 
     
     
       50. An instrument according to  claim 48  wherein said flow controller comprises a solenoid valve and said fluid communication path comprises a tube between said solenoid and said cavity. 
     
     
       51. An instrument according to  claim 44  wherein said detector is an infrared temperature detector. 
     
     
       52. An instrument according to  claim 44  comprising an input device for providing said processor with data selected from the group consisting of microwave power levels, durations of microwave application and setpoint temperatures.